1. Field of the Invention
This invention relates to windmills, generally, and more particularly relates to a windmill construction of the vertical axis type having an upstanding set of rotatably mounted outer blades and an upstanding set of conjointly rotatable inner blades positioned radially inwardly of the outer blades.
2. Description of the Prior Art
Vertical axis windmills in general are well known, of course, and have been described in numerous U.S. and foreign patents.
For example, U.S. Pat. No. 2,515,713, awarded in 1950 to Johnson and other, discloses a mixer device having helical blades of the type that could be adapted for a windmill construction.
U.S. Pat. No. 4,115,032, issued in 1978 to Lange, shows a windmill having blades that rotate about a vertical axis. The Lange device converts the energy of wind into mechanical rotation of an upstanding output shaft for driving an electric generator, a pump, or the like.
A U.S. patent awarded in 1981 to Dereng, U.S. Pat. No. 4,264,279, discloses a self starting wind turbine having a single blade rotatable about a vertical axis.
Another U.S. patent to Lange, U.S. Pat. No. 4,543,042 (1985), discloses a windmill rotor of the vertical axis type having at least three main blades mounted symmetrically around a shaft which blades are bowed to define a generally spherical configuration.
U.S. Pat. No. 4,281,965, awarded in 1981 to Stjernhom, discloses a cantilever mounted wind turbine having an interior stationary support column and a concentrically mounted rotatable rotor.
None of the earlier patents known to the present inventor teaches a windmill having blades constructed out of a metal drum, nor do the patents of the prior art of which the present inventor is aware include mechanisms for maintaining a constant rotational velocity of the type disclosed hereinafter.
It is an important object of this invention is to provide a mechanism that allows rotational movement of windmill blades at a constant, nonsurging speed, which speed is maintained independent of wind speed.
Another object of this invention is to provide a simple method of constructing windmill blades from readily available materials.